Field of the Invention
The present invention relates to an Al alloy cast product containing an Al3Sc precipitation particle in a metal texture thereof, and which exhibits an excellent high-temperature strength, and a method for producing the same.
Description of the Related Art
Aircraft and automobile components are required to have high strength, high heat resistance, and high durability as well as a light weight. Attempts to make such components from Al alloys have been made in view of mass-producing the components at low costs. For example, production of a turbocharger compressor using atomized powder of an Al alloy doped with La and Sc as a starting material is proposed in Japanese Laid-Open Patent Publication No. 2012-510017 (PCT). In this case, the atomized powder is subjected to an HIP (Hot Isostatic Pressing) treatment, and then to an extrusion processing or the like.
In general, this type of component has a complicated shape. In a case where the atomized powder is HIP-treated to produce a sintered body, and then the sintered body is subjected to the extrusion processing in the above manner, the component with a complicated shape cannot be easily produced. Therefore, it is necessary to subject the sintered body to a cutting processing or the like to thereby obtain a final product (the component) with desired shape and size. In addition, also in a case where a powder metallurgy process is carried out using the atomized powder, the component cannot be easily produced with a complicated shape. Therefore, this method does not have a satisfactory production efficiency, and contains a complicated process.
Accordingly, production of the component by casting a melt of an Al alloy has been studied. The casting process is capable of easily producing the component with a complicated shape. Furthermore, the casting process is capable of forming a cast body close in size to the final product. Therefore, this method requires only a simple finish processing such as a burring processing.
Al—Si—Mg alloy (such as AC4CH), Al—Si—Cu—Mg alloy (such as AC4D), and Al—Si—Cu—Mg—Ni alloy (such as AC9A) are known as Al alloys for casting that have relatively excellent high-temperature strengths. The Al—Si—Cu—Mg—Ni alloy (such as AC9A) has a low toughness at ordinary temperature and cannot be easily cast, and therefore is hardly used for the casting process practically.
Among the Al alloys, a particular alloy has been used as a wrought material conventionally, but has been used for producing a cast product in recent years. For example, Japanese Patent No. 4290024 discloses a technology related to a heat-resistant aluminum alloy cast product containing 0.01% to 0.8% of Sc (a thin plaster cast product).
Furthermore, Japanese Laid-Open Patent Publication No. 2011-510174 (PCT) discloses that an Al alloy cast product, which contains an Al3(Sc, Zr) precipitation particle having a particle diameter of about 40 to 60 μm and a Tr phase deposit having a size of about 5 nm in the metal texture, exhibits an effective resistance to hot tearing.